Embodiments of the present disclosure generally relate to a system and method for monitoring eye quality of data.
Non-return-to-zero (NRZ) is a form of digital data transmission in which binary low and high states are transmitted by specific and constant direct current voltages. In positive-logic NRZ, the low state may be represented by the more negative or less positive voltage, and the high state may be represented by the less negative or more positive voltage. For example, a logic state of 0 may be represented by 0.5 volts, while the logic state of 1 may be represented by represented by 1 volt. Conversely, in negative-logic NRZ, the low state may be represented by the more positive or less negative voltage, while the high state may be represented by the less positive or more negative voltage. For example, a logic state of 0 may be represented by 1 volt, while the logic state of 1 may be represented by 0.5 volts. In general, NRZ data includes binary code in which 1s are represented by one significant condition (such as a positive voltage) and 0s are represented by another significant condition (usually a negative voltage), with no other neutral or rest condition.
NRZ data may be displayed with respect to an eye diagram or pattern. In an eye diagram, a data signal from a receiver is repetitively sampled and applied to a vertical input, while the data rate is used to trigger a horizontal sweep. The display is referred to as an eye diagram because the pattern appears as a series of eyes between a pair of rails.
An eye diagram provides an indication of the quality of signals in high-speed digital transmissions, for example. An oscilloscope, for example, may generate an eye diagram by overlaying sweeps of different segments of a long data stream driven by a master clock. When many such transitions have been overlaid, positive and negative pulses are superimposed on each other. When many bits are overlaid, the resulting image appears similar to the opening of an eye.
Eye quality refers to the openness of an eye diagram. A perfect eye diagram is generally open such that all data transitions take place at the same multiples of a unit interval. However, when data transitions occur at different multiples of the unit interval, the quality of the eye diagram diminishes, such that the eye diagram begins to close. While a perfect eye diagram is open, a poor eye diagram exhibits smearing, fuzziness, or other distortions that encroach into (or close) the eye pattern.
Accordingly, assessing the quality of an eye diagram provides information as to the quality of data received by a system. However, known eye quality monitoring devices typically include complex circuits that utilize relatively high levels of power during operation.